Lewis Hamilton admitted he was surprised at staying on Charles Leclerc's tail in Friday's rain-hit free practice for the Italian Grand Prix after the Formula One champion finished just 0.068 seconds behind his Ferrari rival.
Hamilton had forecast that his Mercedes team would struggle to match Ferrari's pace on their home track, but he ended the day believing qualifying and Sunday's race will be closely-fought.
"It's not a massive amount different to how it was at the last race," said Hamilton.
"Obviously, they are quite quick in a straight line, but we're quite strong on race pace... Actually, it looks that we are perhaps a little closer on single lap pace so we may have a fight."
In-form Leclerc completed a 'double top' clean sweep for Ferrari by winning both sessions, delivering a best lap of one minute and 20.978 seconds in the afternoon as he and Ferrari team-mate Sebastian Vettel sandwiched Hamilton between them.
"It's a good day of course, to be first and first, but I believe it looks better on paper than it actually is," Leclerc said.
"What we have done is not the real picture of everything," he added.
Four-time champion Vettel was third, two-tenths of a second down on Leclerc's best and ahead of Valtteri Bottas in the second Mercedes with Max Verstappen and his new Red Bull team-mate Alexander Albon taking fifth and sixth.
"It definitely is surprising. Honestly, I just didn't know what to expect this weekend, apart from them being quick on the straight, which they are, but there are enough corners in which we're able to gain it back," added Hamilton.
"They're not really that quick through the corners, so it kind of balances out. I still think it's going to be a really hard race, but we are on a similar level."
- Mercedes 'opportunity' -
Bottas, who is 65 points behind Hamilton in the drivers championship, was also pleased with his efforts, saying that he believed he and Hamilton have a chance to take pole on Saturday.
"I didn't have a really good tow on my quickest lap, otherwise it felt good," he said. "And (it was) pretty positive on the long runs.
"I think we have an opportunity, yes. We definitely need a perfect set-up from the package we have and a perfect tow -- that's going to be the key."
On a dismal, drizzly day at the Autodromo Nazionale in Monza's old royal park, Ferrari's speed was encouraging for the army of fans hoping to cheer the team to a first home win since 2010.
The first morning session was interrupted by three red-flag suspensions and unusually, after a slow start in difficult conditions, the second session was red-flagged and suspended due to rain after Leclerc had clocked his best lap early on.
The two Mercedes retreated to their garage before emerging again on softs when Hamilton delivered his best lap in the mixed conditions, which are likely to be repeated on Sunday following a fine dry day for qualifying on Saturday.
After seeing Hamilton's pace on Friday, Ferrari team boss Mattia Binotto said that he did not believe they had the all-round performance to overhaul Mercedes even if they win on Sunday.
"Whenever we go to circuits where there are a lot of corners and where grip-limit is important, or maximum down-force will be required to be fast, we are certainly showing our main weakness," he said.
"Can we address that by the end of the season? I don't think so because the gap in that area is too big."